Make the Refried Beans:
Heat the oil in a saucepan large enough to hold the beans later.
Add the onions and salt and ground black pepper and saute for a few minutes until the onion starts to soften. Add the garlic and continue to cook over low heat for another 2-3 minutes.
Add the chipotle chili and cumin powder and stir well to mix.
Add the cooked beans along with 1 1/2 cups of the cooking liquid or water or vegetable stock.
Bring to a boil and turn down the heat to a simmer. Let the beans cook about 10 minutes. If they get dry, add more water or stock.
Using a potato masher, mash the beans until some are completely mashed and others are still whole or have some texture.
The finished beans should have a thick, slightly soupy texture. They will thicken further as they stand, so this is important.
Stir in the coriander leaves.
Make the Mango-Basil Salsa:
Mix all the ingredients and set aside 30 minutes for flavors to merge.
Assemble the Mollete:
Take the lower half of the bolillo bread and scoop out some of the crumb-- I like to do this so I can get more filling inside, but if you don't want to do this, that's fine too.
Toast the bolillo until the edges are just turning crisp.
Slather on some of the refried beans, top with the mango salsa, and serve immediately.